Vertical scanning antennareflector system



Nov. 309A 1948.

A. G. KANDolAN VERTIQAL :SCANNING ANTENNA-REFLECTOR SYSTEM i 1 Filed May '7, 1945- l observer.

Patented Nov. 3o, 194s UNITED STATES :PATENT MERTICAL SCANNINGANTENNA- y @RE-FLECTGR .SYSTEM ArniiglG. w"Kardoan,"New York; NSY.,4 assignorto -Federal Telephone-and Radio Corporation, New Yorl{,'N."fY.,-JafcorporationsofDelaware pplication-May 7, 1945,.Scil,No.592,409

2f Claims. (Cl. Z50-332657) AThis .invention relates 'to radio antennas 'and moreparticularly to .a radiating antenna array `which isthe means for carryingout anelective method "for "producing `an improved intermediate 'angular zone vertical field pattern.

"In certain applications ofthe radio communicationfart and particularly in radio `obstacle detection systems, periodically transmitted impulses Awhich are ireflectedfrom the objects 4to be located, areemployed, -for instance, intl-coating aircraft approaching at` variousheights and angleswith respectlto an observer.

",Inprevious vsystems of thisitype it was found ,that at cerytaingiven` frequencies .-of transmission vertical coverage 'Was obtained by means of var# ious antennaarrays which Wereeffective in covering an'angle with respect to the horizon from the horizontal upto aboutlO-to l5 degrees.

These previous systems clearly Vlackedan ade- Tqnate2field#coverageiforiaircraft approaching toward the observer, that is, onachang'ing its langle with the horizontal frornla low valuesay from 15 degrees to an angle increasing to 60 degrees as it approached and passed theiebserver.

lIn view` of the aforesaidconditions in the prior art, various-methods Were-tried in order to beable tofffollowan approaching plane as its angle with the horizon increased .at its approach .toward the One method such as the Variation of a given transmitting frequency is effective in causing the displacement in a vertical plane of a high intensity portion of a given vertical radiation pat# tern from a position of low angularity toward the vertical. However, variation inA frequency of this type with conventional antenna arrays required apparatus, which became rather complicated if certain other necessary requirements were to be met. This drawback resulted in the preference for so-called antenna arrays involving a radiator with a paraboloid reector. This, too, however, did not provide an .adequate coverage of the desir-able angular zone `as it lacked in its radiation pattern the required vertical directivity.l

It is accordingly an object of this invention to provide an antenna array Whi-ch produces a radia angular zone by progressively displacing a direct-l ed portion of a given radiation pattern.

in accordance With'a feature of myy invention'fI provide an `array whichV consists 'off-a radiator and aeiiector'which in aparticular case'may befof modified paraboloidal fornL This particular form `rmayberegardedas4 adished paraboloidfffrom which .there has A'losen cuts-away Aai-segment from an 'outer 'edge 'and the corresponding "surface This configuration `of thejreflector-withA :the cutaway sector disposed on thetop causes a'bulgingout of "a tvertic'al' field 'intensity floop which locate'din theinterrnediateangular zone betweenil5 and' degrees with -respect -to the horizontal. This middle angle loop `of the radiation 7pattern in "accordance with-'myinvention'may `lo'e'vari'ed in `the location of its maximum'intensityfrom'the lower portiono'f this zone' toward the vertical by means'of "avaria'tion-in the transmittingjfrequency causing asuccessive scanning of the entire middle angleizone. Thus, any craft' approaching toward or receding from the 'observermay *be 'closely .and "successivelyfollowed at the point of observation.

"These and :otherieatures` andpbjectsof 4thel invention'fwill become 'apparent' uponY consideration `ofthe following detailed description of an emlcodimentpof' the invention to be 'read in connection with the accompanying drawings in which Fig. 1 is a representation, partly in diagrammatic and partly in perspective form of a transmitter and an antenna array incorporating the present invention; and

Fig. 2 illustrates a type of radiation pattern obtainable with the transmitter of Fig. 1.

Referring to Fig. 1, a transmitter is indicated at l which by means of a connecting link 2 supplies radiating energy to a radiator or antenna 3 which is shown lsupported in a horizontal plane on an antenna tower 4 and which is disposed at the focus of` a dished metallic paraboloid reflector 5. The reilector 5 has a section thereof cut away at 6, the cutting plane being parallel to the axis, the resulting edge being shown disposed parallel to the ground. The cut-away portion of the reector 5 is indicated at 1 in broken lines. 'I'he transmitter may be provided with a means for adjusting its transmission frequency at 8.

The radiation pattern as obtained with the antenna array 3 5 ofFig. i is shown in Fig. 2, where the relative vertical eld intensity is shown as a relation of distance to the angle of elevation from the horizontal. The observer at the location of the transmitter is to be visualized at a point S, an aircraft Ii! being shown approaching the transmitter in the direction indicated by an arrow I l. The vertical radiation pattern as produced by the array of Fig. 1 is indicated by the solid line dening an envelope l2. A dished paraboloid not formed in accordance with the invention would produce a pattern showing relatively small eld intensities in the angular Zone from 20 to approximately 80 degrees as suggested by the broken lines at I3, the actual maximum distance covered by the field being somewhat more extensive in the horizontal, that is, in the lower angular Zone than shown.

In contrast thereto the additional vertical directivity obtained in the vertical radiation pattern due to the cut-off of segment 'l increases the relative field strength in this angular Zone as indicated by the projection I4 in the general field pattern. By varying the frequency of the transmitter 8, the projection It representing the relative increased strength in a given angular zone may be moved along the dot-dash line I5 to enable the operator of the transmitter to cover substantially the entire middle angular zone between degrees 2O and 80, whereby an approaching or receding plane with respect to the observer at 9 may be followed on the observation screen of the detection system without the difiiculties inherent in-v a regular paraboloid reflector.

The principle underlying this invention may be expressed in one manner by saying that the vertical eld due to a given array is to be distorted or reshaped in such a way that while the power output remains substantially constant the horizontal distance covered by the vertical field has been cut in extent, the surplus power thus made available being diverted to increase the eld intensity in the middle zone.

While I have shown a preferred form and methodof a directed distortion of the radiation pattern of a reflector array, it is of course apparent that the radiation pattern may also be distorted by other shaping of the reflector so long as it enables the desired production of vertical mitter as above-mentioned. However, in this application, a preferred and simpler form has been illustrated wherein the antenna has been placed at the focus of the paraboloid and an increased directivity is obtained by means of the formation of the reilector, the variation in frequency serving as a means for effectively scanning the middle angular zone. y I

While I have described above the principles of my invention in connection with specific apparatus it is to be clearly understood that this description is made only by way of example and not as a limitation on the scope of my invention as indicated in the objects and defined in the accompanying claims.

What I claim is:

1. A method for scanning a given vertical angular zone by'means of the electromagnetic radiation of a transmitter, comprising producing a given vertical pattern at a given frequency and at a constant power output, introducing a distortion in said pattern to improve the relative eld intensity in a given angular zone by diverting radiating power to said zone, and progressively varying the frequency of transmission, whereby said distortion progressively changes its position with the 'change in frequency to scan said given zone.

2. An electromagnetic radiating energy system comprising a dished paraboloidmetallic reflector having a segment thereof cut away on a plane parallel to its axis, a radiator disposed at the focus of said reflector, means operatively connected to said radiator for processing energy for radiation, said processing means comprising means for varying the frequency of transmission.

ARMIG G. KANDOIAN.

- REFERENCE?,` CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,156,653 Ilberg May 2, 1939 2,260,273 Hahnemann Oct. 21, 1941 2,270,965 Peterson Jan. 27, 1942 

